Impedance matching of an electrical load to the impedance of a signal source and the characteristic impedance of a transmission line is often necessary to reduce reflections by the load back into the transmission line. As the length of a non-terminated transmission line increases, reflections become more and more problematic. When high frequency signals are transmitted or passed through even very short transmission lines, such as printed circuit board (PCB) traces, a resistive termination is typically inserted at the load to avoid reflections and degradations in performance.
When the load comprises one or more integrated circuit devices, the terminal resistor may be either internal or external to the integrated circuit device. The placement of a resistor outside an integrated circuit device results in an additional stub or short transmission line between the resistor and the integrated circuit device. External resistors are also relatively bulky, and so they undesirably increase the required footprint or area for an application. On the other hand, resistors which are internal to an integrated circuit device do not allow for the flexibility of being removed. This is of particular concern when multiple integrated circuit devices are being fed by the same signal along a common transmission line, because the source and transmission line will see a parallel combination of the internal resistors, resulting in an impedance mismatch. Furthermore, when a signal is transmitted or passed to multiple integrated circuit devices, the transmission line along which the signal passes typically must bend, curve, or turn around each integrated circuit device. These bends, turns, and curves can cause impedance discontinuities in the characteristic impedance of the transmission line, and further result in impedance mismatches.
Thus, there is a need for an integrated circuit resistive end termination and transmission line routing system for applications incorporating integrated circuits on a PCB that provides for accurate impedance matching, minimal reflections, efficient signal routing, and a minimal application footprint.